velocity of particle is given by v=(4-t)m/s.find the distance travelled by the particle in 6 seconds

Hint: remember that the distance traveled is the area under the velocity versus time graph. If you're familiar with methods of integration it's real simple. If not, then I suggest you plot the function v=4-t from t=0 to t=6, and calculate the area. Post back with your attempt and we'll check it for you.